Tangent Theorem: if a line is tangent to a circle, then the line is perpendicular to a radius of the circle drawn to the point of tangency.
external image 2606.gif
Tangent: a line in the plane of the circle that intersects the circle at exactly one point.
external image image076.jpg
Chord: Segment whose endpoints are on the circle.
Secant:A line that intersects a circle at two points.
Radius and Chord Theorem: A radius thats perpendicular to a chord of a circle bisects the chord.
Converse of tangent theorem: If a line is perpendicular to a radius of a circle at its endpoint then it is tangent to the circle.
2 tangents
2 tangents
Secant
Secant
2 Chords
2 Chords


Perpendicular Bisector and Center Theorem: the perpendicular bisector of a chord passes through the center of the circle

Theorm 9.2.5- the perpendicular bisector of a chord passes throught the center of the circle.

Question: What is the measure of a angle that is made of a line perpendicular to the radius?